Winchester Bay is an unincorporated community in Douglas County, Oregon, United States. For statistical purposes, the United States Census Bureau has defined Winchester Bay as a census-designated place (CDP). The census definition of the area may not precisely say yes to local treaty of the area with the similar name. The population of the CDP was 382 at the 2010 census. The community of Umpqua City was customary in 1850.

According to the United States Census Bureau, the CDP has a total Place of 3.1 square miles (8.1 km), of which 2.3 square miles (6.0 km²) is estate and 0.81 square miles (2.1 km), or 26.24%, is water.

As of the census of 2000, there were 488 people, 238 households, and 139 families residing in the CDP. The population density was 183.6 people per square mile (70.8/km²). There were 362 housing units at an average density of 136.2 per square mile (52.5/km). The racial makeup of the CDP was 96.11% White, 1.43% Native American, 0.41% Asian, 0.20% from supplementary races, and 1.84% from two or more races. Hispanic or Latino of any race were 1.43% of the population. There were 238 households, out of which 16.8% had children under the age of 18 living next them, 50.8% were married couples buzzing together, 4.2% had a female householder next no husband present, and 41.2% were non-families. 36.6% of anything households were made occurring of individuals, and 20.2% had someone animate alone who was 65 years of age or older. The average household size was 2.01 and the average relations size was 2.57.

In the CDP, the population was 16.8% under the age of 18, 7.6% from 18 to 24, 18.9% from 25 to 44, 27.5% from 45 to 64, and 29.3% who were 65 years of age or older. The median age was 50 years. For every 100 females, there were 116.9 males. For all 100 females age 18 and over, there were 120.7 males. The median allowance for a household in the CDP was $30,139, and the median pension for a intimates was $37,292. Males had a median pension of $30,625 versus $22,321 for females. The per capita pension for the CDP was $17,307. About 17.9% of families and 21.3% of the population were under the poverty line, including 38.1% of those below age 18 and 6.3% of those age 65 or over.